1. Field of the Invention
This invention relates to a force-operated suspension position sensor for an automotive vehicle.
2. Disclosure Information
Automotive suspensions employing adjustable suspension units typically utilize one or more sensors for detecting the position of one or more portions of the suspension with respect to either another part of the suspension itself or another part of the chassis of the vehicle. In the case of vehicles using load leveling or air or hydropneumatic suspension systems, it is necessary to know the ride height of the vehicle in order to determine whether correction of the ride height is required. In the event, for example, that, the ride height is lower than a prescribed "trim" limit, as determined by the height sensor, an adjustable suspension unit may be given a command to increase ride height. Conversely, in the event that the ride height exceeds the prescribed "trim" limit, the adjustable suspension unit may be given a command to lower, or decrease, the ride height.
Vehicular height sensors are useful not only with ride height adjusting systems but also as transducers for use with adjustable suspension dampers. A sensor according to the present invention is useful for providing not only suspension position information but also ride height information for use with a vehicle leveling system or an air or hydropneumatic adjustable suspension or other type of adjustable suspension system.
U.S. Pat. No. 4,105,216 discloses a motor vehicle level control circuit in which a pair of optical detectors interacts with a rotary shutter device to produce a first logic signal pair when the vehicle's ride height is in a trim region, and second and third logic signal pairs when the vehicle's ride height is either high or low and out of the trim region. The system of the '216 patent has the capability of producing only three logic signal pairs with two detector devices. A sensor according to the present invention, however, will have the capability to produce, with only a single detector or transducer device, a continuously variable output defining a great number of ride height states.
U.S. Pat. No. 4,453,725 discloses a rotary height sensor using a bifurcated shutter and three optical devices in order to produce a sensor capable of resolving vehicle ride height into five levels.
U.S. Pat. No. 4,433,849 discloses a vehicle leveling system having two reference vehicle ride height positions requiring separate detectors for each reference ride height position.
U.S. Pat. application Ser. No. 126,082, filed Nov. 27, 1987, which is assigned to the assignee of the present invention, discloses a vehicle height sensor in which two detector devices are used to produce a digital output having four discrete states.
A variety of sensing techniques have been employed with vehicular height sensors. These include, without limitation, electro-optical devices, linear variable differential transformers, and Hall Effect devices. Examples of the latter are disclosed in U.S. Pat. Nos. 3,473,109; 4,107,604; 4,204,158; and 4,555,120.
A sensor according to the present invention may be used beneficially in conjunction with an operator for controlling the ride height of an automotive vehicle. U.S. Pat. Nos. 4,105,216; 4,453,725; 4,540,188; and 4,568,096 all disclose ride height control systems which track the amount of time the system spends in a high or low position on either side of a trim band. It is also known to control suspension ride height by taking an average of the amount of time the suspension spends above or below a trim band. None of the previously described systems, however, calculates a weighted average which takes into account the magnitude of the suspension's excursion either above or below the trim band or region. Accordingly, it is an object of the present invention to provide a system which tracks and calculates a weighted average ride height so as to provide a more precise measurement of actual ride height upon which to base corrective action.
It is an object of the present invention to provide a high resolution suspension position sensor capable of accommodating a plurality of reference vehicle ride height positions with a single height sensor containing only a single detector.
It is an advantage of the present invention that a suspension position sensor according to this invention will furnish much more information than prior art sensors having a greater number of detector devices.
It is a further advantage of the present invention that a system comprising a plurality of sensors according to the present invention and used for controlling the ride height of a vehicle may be calibrated with ease during the installation of the sensors by merely placing the vehicle at a reference ride height and by placing in the memory of an electronic processor associated with the sensors a signal for each of the sensors corresponding to the reference ride height. This will automatically compensate for manufacturing differences in the sensors and in the mounting hardware of the sensors.
It is a further object of the present invention to provide an adjustable ride height suspension unit operator and sensor for controlling the ride height of an automotive vehicle which utilizes a weighted averaging technique for determining when correction of the ride height is warranted.
Other objects, features and advantages of the present invention will become apparent to those skilled in the art to which the present invention pertains.